Repeating coil



F. E. FIELD RBPEATING 0011.

June' 12.11923,-

Filed July 26. 1922 Fra Patented June 12, 1928.

- N D- TATES PATIENT OFFICE. f

115mm: E. FIELD, or SOMERVILLE, NEW, JERSEY, VASSIGNOR 'ro WESTERNELECTRIC v HCOMPANY, mconrona'rnn, on NEW YORK, 11. Y., A CORPORATION01' NEW YORK.

REPEATING c011,.

Application filed July 26,

This invention relates to balanced translating circuits and pertains,especially to means for preventing unbalance and distortion in a speechtransmission circuit in which i 6 transformers are employed forconnecting a tween the cores and the casing are practi cally negligiblewhereas the capacities between the adjacent layers of the superposedcoils have considerably larger values which cannot be neglected.

It isan object of'this invention to materially reduce 'in transformersof the above and similar types, the effect ofthe capacities between-theprimary and secondary windin 1 A nother object of the invention is tosubstantially eliminate the effect of the capacities between theprima'rv and secondary 25 windingsof the input transformer;-

These objects are attained in general. by connecting the grids of theassociated vac uum tubes to the layers of the secondary sections of theinput'transformer which are non-adjacent to the primary sections of thetransformer and by connecting the'cathodes of the tubes to the layers ofthe-secondary sections which'are adjacent the primary. The anodes of thetubes are connected to the non-adjacent layers of the primary sectionsof the output transformer and the cathodes to the adjacent lavers of theprimary through a battery. The outer layers of the primary oftheinputtransformer are connected so as to be in the-electrical centerof the primary, and are therefore maintained at a substantially constantpotential with'respectto ground when the winding is connected to-a'balanced circuit such as an 45 open wire'line The cathodes are groundedThe etfect' of this arrangement thus is to short-circuit the interlayercapacities through ground. j I

Referring now to the accompanying drawings, Fig; '1 discloses thewinding of the transformers and their connections to the repeaters, andFig. 2 is a diagrammatic represent-ation thereof. r

i The circuit of this invention comprises a transformer B, the primaryof which is con-' 1922. Serial No. 577,522.

nected to an incoming line A which is balanced with respect'to groundand the secondary of which is included. in the input circuit of abalanced vacuum tube repeater circuit C, the output'circuit of whichincludes the primary of a transformer D, the secondary of which isconnected to an outgoing line E.

The input transformer may comprise a substantially rectangular frame 1around the ends 2 and 3 of which are wound multilayer primary coils4'and 5. Surrounding the coils 4 and 5 and having their inner layersadjacent the outer layers of said coils are multi-layer secondary coils6 and 7 which cooperate with the coils 4 and 5 to formthe primary andsecondary of the transformer.- Bindingposts 8,9, 10 and 11 are providedfor the inner and outer layers of the primary coils 4 and 5. For theinner and outer layers ofthe secondary coils 6 and 7 are provided thebinding posts 12, 13, 14 and 15. The binding posts 9 and 10 areconnected to the incoming line and a conductor 16 con nects the bindingposts 8 and 11. The con ductor 16 by virtue of its symmetrical po- 8sition with respect to the incoming line of the circuit is maintained ateffective ground potential becauseof the capacities to ground of the twomembers of-the incoming line. The binding posts 13 and 14 ofthesecondarycoils are connected bya conductor 17 and the binding posts 12 and areconnected, respectively. with the grids 18 and 19 of the repeater tubes20 and 21. The cathodes 22 and '23 of the tubes 20'and 21 are in circuitwith the battery24 which supplies heating current to the cathode I andare grounded at 25. The conductor 17 is connected to the negative poleof the battery 28. The output"transformer for this circuit may comprisea substantially rectangular frame 31 around the ends 32 and83 of whichare wound multtlayer secondary coils 34 and 35; Surrounding the coils 84and 35 and having their inner layers adjacent the outer layers of saidcoils are multi-layer primary coils 36 and 37' which cooperate with thecoils'34 and 35 to'form the primary and secondary of a step downtransformer. Bindingposts 38, 39, 40 and 41 are provided for the innerand outer layers of the primary coils 36 and 37.v For the inner andouter layers of the secondary coils 34 and 35 are provided the bindingposts 42, 43, 44 and 4-5. The binding posts 39 and 40 are con nected bythe conductor 46' to: the cathodes 22 and 23 through a low impedancebattery 47 of relatively small voltage. The binding.

posts 38 and 41 are connected, respectively,

to the anodes 26 and 27 of the tubes and.

21. The binding posts 43 andist are connected to the outgoing line andthe binding posts 42 and 45 are connected by conductor 48 which, becauseof its symmetrical: position with respect to the outgoing line of thecircuit, is maintained at effective ground potential by virtue of thecapacities to ground of the two members oi 'the outgoing line.

Fig. 2 discloses, diagrammatically, the effect of this method ofconnection upon the capacities between the adjacent layers of theprimary and secondary coils of the input and: output transformers. Thoseportions of the: coils adjacent the binding posts 8 1 1, I2 and 1 5represent-the outer layers of coils 4, 5,6 and 7,. respectively, andthose portions adjacent the'binding posts 9, 10. 13 and 14 represent theinner layers of said coils 4, 5,

6 and 7 respectively. The capacities F and F are therefore convenientlyrepresented as being between the outer ends of coils 4 and5 and theinner ends of coils 6 and 7,.respec tively. Since the terminals 8 and13, and 11 and 14 of the capacities F and F are connected to'the groundpotential member 16 and to ground 25, respectively, theeffect of thesecapacities is nullified to such. an extent that they h'avecno effectupon the transmission' of speech waves.

In the output transformer, those portions of the coils adjacent thebinding posts 38. 41,- 42 .and 45 represent the outer layers of thecoils 34, 35. 36 and 37, respectively, and those portions adjacent thebinding posts 39, 40,- 43 and 44: represent the inner layers of saidcoils 34, 35, 36 and 37, respectively. The

capacities G and G are therefore conveniently represented as beingbetween the innor end of coil 34 and the outer end of coil 36, andbetween the inner end of coil and the outer end of coil 37,respectively. Since the terminals 4-2-and 45 are connected to the Iground potential member lS and the terminals 39,.and 40 are maintainedat a potential iii) .in excess of ground equal only to the potenforkeeping the adjacent layers of the priprising a multi-layer primary coiland a mary coils of each section at a fixed potential with respect toground.

2. In a transmission'circuit, a transformer having a pair of sections,each section commulti-layer secondary coil surrounding said primarycoil, a connectionbetween the outer layers of the primary coils,connections from thei nnerlayers of the primary coils to a line the twosides of which have like capacities to groundwhereby said firstmentioned connection is at a fixed potential with respectto ground, apair of vacuum tubes, each having a cathode and a grid, connections-be-' tween the outer layers of the secondary coils and the grids ofsaid tubes, and connections between the inner layers of the secondarycoils and-the cathodes of said tubes,said last named connections beinggrounded.

In a'transmission circuit, a transformer comprising coaxial multi-layerprimary andsecondary windings-insane including connections from saidwindings to a line having like capacities between its two sldes andground for maintaining the layer of the said connections at fixedpotentials with respect to ground, said means lncludingaconductive pathbetween one of said connections and ground. and electrical paths.from'the coils joined by the other. connection to line having its twosides similarly capacitatively related to ground.

5. In a transmission circuit, a transformer comprising a pair ofmulti-layer primary coils in series, means tor'keeping the ter- -minalsof the outer layers of each'ot said coils at substantially groundpotential, said means includingconnectionsfrom the inner layers of saidprimary coils to a line having like capacities between its two sides andground, a pair of multielayer secondary coils surrounding said primarycoils respectively, and connections between the terminals of the innerlayers thereof and ground.

6. In a signaling circuit, a balancedtrans, mission line, a transformercomprising a pair of multi-layer primary coils connected in series and apair of multi-layer second ry coils coaxial with and surrounding saidprimary coils, said'secondary coils being connected in series,connections from the inner to said transmission line and connectionsfrom the inner layer of each section of the secondary to an electricaldevice. said last named connections being grounded.

7. In a transmission circuit, a transformer comprising a pair ofsections, each section comprising a primary and secondary coil arrangedwith the outer layer of one adjacent the inner layer of the other, aconnection between the layers of said primary coils adjacent saidsecondary coils, means for maintaining said connection at substantiallyground potential. said means including connections from the inner layersof said primary coils to a line having like capacities between its twosides and ground, a pair of vacuum tubes, each having a cathode and agrid, connections between the gridsof said tubes and the non-adjacentlayers of said vsecondary coils, and connections between the cathodes ofsaid tubes and the layers of said secondary coils adjacent said primarycoils, said last named connection being grounded. 8. In a transmissioncircuit. a line having terminals substantially balanced with re spect toground, a transformer comprising a pair of multi-layer primary coils,said coils having the terminals of their inner layers connected totheterminals of said line, a connection between the terminals of theirouter layers, said last named connection bcing at a fixed potential withrespect to ground, and a pair of secondary coils superposed on saidprimary coils. the inner layers of said secondary coils being connectedto ground through a path of low impedance.

9. In a transmissioncircuit. in combination, an' incoming line.a't-ranstormcr com- ,prisng a plurality of primary windingssymmetrically. arranged across the incoming line, connections betweenthe outer layers of said primary windings. means including said line formaintaining said connections at sub- ,stantially ground potential, amulti..-layer secondary comprising a plurality of windings surroundingsaid primary windings, a plu rality of vacuum tubes. each having acathode and a grid, connections between the outer layers of saidsecondary windings and the grids of said vacuum tubes. and connectionsbetween the inner layers of said secondary windings and the cathodes ofsaid tubes, said last named conncctionsbeing grounded.

10. In a transmission circuit, a trans former having a plurality ofsections, each tween its two sides and ground whereby saidconnection ismaintained at substantially ground potential, a pair of vacuum. tubes,each having a cathode and a grid, connections from the layers of thesecondary coils non-adjacent said primary coils to the grids of saidtubes, and connections from the layers of the sections of said secondaryadjacent said primary coils to the cathodes of said tubes, said lastnamed connections being grounded.

11. In a balanced transmission circuit, an outgoing line, a transformercomprising a pair of multi-layer secondary coils, the terminals of theouter layers of said secondary coils being connected together,connections between the terminals of the inner layers of said secondarycoils and said outgoing line, a pair of multi-la-yer primary coilssurrounding said secondary coils, a pair of vac uum tubes, each having acathode and an anode, connections between the terminals of the innerlayers of said primary coils and the cathodes of said tubes, connectionsbetween the terminals of the outer layers of said primary coils and theanodes of said tubes and connections between the cathodes of said tubesand ground.

12. In a balanced transmission circuit, a pair of vacuum tubes, eachhaving a cathode and an anode, an output transformer comprising a pairof Inulti-layer primary sections and a pair of multi-layer secondarysections, connections between the anodes of the tubes and the terminalsof the layers of the primary sections non-adjacent the sec .ondarysections, connections between the FRANK E. FIELD.

